linux-kernel - Re: [PATCH v9 00/14] Add support for remote unwind

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Date:	Wed, 8 Jun 2016 15:33:22 +0800
From:	Hekuang <hekuang@...wei.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>
CC:	<peterz@...radead.org>, <mingo@...hat.com>,
	<alexander.shishkin@...ux.intel.com>, <wangnan0@...wei.com>,
	<jpoimboe@...hat.com>, <ak@...ux.intel.com>, <eranian@...gle.com>,
	<namhyung@...nel.org>, <adrian.hunter@...el.com>,
	<sukadev@...ux.vnet.ibm.com>, <masami.hiramatsu.pt@...achi.com>,
	<tumanova@...ux.vnet.ibm.com>, <kan.liang@...el.com>,
	<penberg@...nel.org>, <dsahern@...il.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 00/14] Add support for remote unwind

hi

在 2016/6/8 3:44, Arnaldo Carvalho de Melo 写道:
> Em Fri, Jun 03, 2016 at 09:06:29AM +0200, Jiri Olsa escreveu:
>> On Fri, Jun 03, 2016 at 03:33:09AM +0000, He Kuang wrote:
>>
>> SNIP
>>
>>> For using remote libunwind libraries, reference this:
>>>    http://thread.gmane.org/gmane.linux.kernel/2224430
>>>
>>> and now we can use LIBUNWIND_DIR to specific custom dirctories
>>> containing libunwind libs.
>>>
>>> Acked-by: Jiri Olsa <jolsa@...nel.org> for most patches except:
>>>
>>> v9:
>>>   - Change function unwind__register_ops() to static.
>>>   - Move up unwind__prepare_access() in thread__insert_map() and save
>>>     map_groups__remove() call.
>>>   - Enclose multiple line if/else into braces.
>>>   - Fix miss modified function declaration for unwind__prepare_access()
>>>     in patch 10.
>> for patchset:
>>
>> Acked-by: Jiri Olsa <jolsa@...nel.org>
> Ok, I'm applying it, after fixing 'perf test unwind', 'perf top --call-graph dwarf'
> and 'perf trace --call-graph dwarf', but I have one question, is the
> scenario where we collect on a x86_64 machine and want to do analysis on
> a ARM64 or x86-32 machine supported? This should be the odd case now,
Yes, it's supported.

But I never tested this before, so I just compiled libunwind for
aarch64, and tested unwinding i686 perf.data on aarch64. Then I
found another issue I've considered but missed at some version of
this patch series.

In util/unwind-libunwind-local.c, PERF_REG_SP/IP is used, but
those macros are assigned to the host platform, we should
redefine them in the wrapper file, for example in
"util/libunwind/x86_32.c".

After fixing this problem, i686 perf.data can be parsed on
aarch64 machine.  Since you've already applied the v9 patches,
should I send patches based on the lastest tree as bug fixes or
just update v9 patches?

Thank you.

Here is the modified part:

diff --git a/tools/perf/util/libunwind/arm64.c 
b/tools/perf/util/libunwind/arm64.c
index 4fb5395..8a5c2fc 100644
--- a/tools/perf/util/libunwind/arm64.c
+++ b/tools/perf/util/libunwind/arm64.c
@@ -29,6 +29,11 @@
  #ifdef NO_LIBUNWIND_DEBUG_FRAME_AARCH64
  #define NO_LIBUNWIND_DEBUG_FRAME
  #endif
+
+#undef PERF_REG_IP
+#undef PERF_REG_SP
+#define PERF_REG_IP PERF_REG_ARM64_PC
+#define PERF_REG_SP PERF_REG_ARM64_SP
  #include "util/unwind-libunwind-local.c"

  struct unwind_libunwind_ops *
diff --git a/tools/perf/util/libunwind/x86_32.c 
b/tools/perf/util/libunwind/x86_32.c
index d98c17e..de21a39 100644
--- a/tools/perf/util/libunwind/x86_32.c
+++ b/tools/perf/util/libunwind/x86_32.c
@@ -31,6 +31,11 @@
  #ifndef NO_LIBUNWIND_DEBUG_FRAME
  #define NO_LIBUNWIND_DEBUG_FRAME
  #endif
+
+#undef PERF_REG_IP
+#undef PERF_REG_SP
+#define PERF_REG_IP PERF_REG_X86_IP
+#define PERF_REG_SP PERF_REG_X86_SP
  #include "util/unwind-libunwind-local.c"

  struct unwind_libunwind_ops *


> but from a quick look I couldn't see this as being supported, is that
> true or I was just lazy not to have tried this?
>
> - Arnaldo